nfs-write-verifier · shipping · also NFSv3 write verifier, writeverf3

NFS write verifier

An NFSv3 write verifier is a server cookie returned by WRITE and COMMIT that lets clients detect state changes that may have lost uncommitted writes.

The verifier distinguishes server states relevant to buffered-write recovery; it is not a data checksum, transaction identifier or cryptographic authentication token. When a returned verifier differs from the one associated with uncommitted buffers, the client retransmits those buffers and establishes stable completion again. Verifier comparison accompanies status, byte-count and stability checks; equality alone does not establish that a write was stable.

Relations

related

nfs-storage, nfs-commit, io-timeout

Limitations

• Detection requires retained client state and does not itself supply or repair lost data. [1]

Citations

1. B. Callaghan, B. Pawlowski and P. Staubach. NFS Version 3 Protocol Specification. RFC 1813, June 1995, sections 3.3.7, 3.3.21 and 4.8. (accessed 2026-10-12)
2. NFS stable writes: what COMMIT, flush and FUA actually promise (accessed 2026-10-12)

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